The subject invention applies to screw drivers of all types, whether of the Phillips type or otherwise. Moreover, the invention has general application to all types of tools which are similarly constructed and utilized as the common screw driver. The variations on the common screw driver are manifold, and it would be too cumbersome to delineate all such modifications herein. Therefore, the invention, as stated in the following discussion will be approached generically, with a specific application and preferable embodiment set forth hereinafter.
Screw drivers, and the like, are common tools used frequently in households and work situations. Their relative utility is unquestioned. The ability to use implements and fastening devices in the form of screws is unquestionably far superior to the use of the common nail since the nail is rather difficult to extract once in place.
The common screw driver employs a handle permanently affixed on a shaft bearing the working tool. The handle is conventionally a cylindrically shaped member, the longitudinal central axis of which is concentrically aligned with the longitudinal central axis of the screw driver shaft. This cylindrically shaped handle member usually has a diameter which is larger than the diameter of the screw driver shaft, and generally the diameter may range as much as ten times, more or less, than the shaft diameter.
This relatively larger diameter of the handle, as discussed above, provides a small mechanical leverage to facilitate the turning movement of the particular screw driver. Moreover, the relative ratio of the radius of the handle (R1) to the radius of the shaft (R2, as set forth in FIG. 1 of the drawings, gives a ratio of R1/R2. The formula W=(F) (2R) provides the basic mathematical relationship of leverage forces in screw drivers where W=Work; F--Force applied to the handle; and R=the effective radius of the particular handle. The larger the effective radius, as determined by the ratio R1/R2 the less force is required to be applied to the handle in turning movement to manipulate the particular screw driver.
In some circumstances where a conventional screw driver is utilized so as to loosen a rightly impacted screw, the leverage attained by existing R1/R2 is not sufficient to yield the force to unloosen a screw, given a fixed turning pressure of the hand. In some cases when more force is applied the screw driver shaft strips the screw head causing it to be permanently damaged, and thus much more difficult to extract in such damaged state. If the effective leverage ratio R1/R2 is increased, this would enable the user to extract or implant screws by using less force. This invention is thusly directed to this objective.